Some X-ray CT apparatuses using photon counting to detect photons of X-rays classify the photons received by a detector into respective energy bins. Such an X-ray CT apparatus using photon counting can generate an image for each energy bin.
Unfortunately, the count of photons in each energy bin may be insufficient for the generation of an image having less noise. In such a case, some or all of the images generated for the respective energy bins are noisy.